Hydraulic balancing control valve and ride control system incorporatng same

ABSTRACT

A balancing valve includes four ports. While the pressures at a pair of balancing ports of a hydraulic balancing valve are equal, the valve maintains two other ports in a closed position. Upon a pressure differential between the balancing ports, fluid communication can occur between one of the balancing ports and either of the other ports based upon the direction of the pressure differential. A hydraulic ride control system utilizes the balancing valve together with other control valves to provide ride control functionality.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims the benefit of priority to U.S.Provisional Patent Application No. 62/658,937, filed Apr. 17, 2018, andentitled, “Hydraulic Balancing Control Valve And Ride Control SystemIncorporating Same,” which is incorporated in its entirety herein bythis reference.

TECHNICAL FIELD

This patent disclosure relates generally to a hydraulic control valveand, more particularly, to a hydraulic balancing valve for controllingthe pressure between two ports and a ride control system utilizing thebalancing control valve.

BACKGROUND

Machines such as skid steer loaders, wheel loaders, telehandlers,tractors, etc., can include one or more actuator configured toselectively manipulate an implement such as a bucket. Typically, suchactuator is a hydraulic actuator or cylinders controlled via a hydraulicactuator control system. The hydraulic actuator control system caninclude a combination of valves used to control the movement of thehydraulic actuator of the machine.

When carrying a load of material with an implement such as a bucket, theentire machine or the implement may bounce when encountering rough oruneven terrain or other obstacles. In order to reduce the bouncing, somemachines are configured with a ride control system having an actuator toabsorb pressure fluctuations in the in the actuators operativelyassociated with the implement. In doing so, it is typically desirable tomaintain the pressure in the accumulator at the same pressure as that atthe head or base end of the actuator.

Hydraulic ride control systems for material moving machines haveutilized many different configurations. In some systems, a plurality ofsolenoid activated control valves are utilized to control the flow ofhydraulic fluid between a pump, a tank, an accumulator, and one or morehydraulic cylinders. A solenoid activated control valve can control theflow of hydraulic fluid between the accumulator and the base end of theactuator to eliminate pressure differences between the two components.Each control valve can present a plurality of possible leak points andthe solenoids can present possible control system faults.

A less complex ride control system can be provided through the use of anorifice between the accumulator and the base end of a hydrauliccylinder. Such an orifice system results in a soft, cushy or bouncy feelassociated with the material moving linkage as a result of the open pathbetween the accumulator and the hydraulic cylinder. The feel of thelinkage can be adjusted by controlling the size of the orifice but withthe tradeoff of reducing the effectiveness of the ride controlfunctionality.

In still another even less complex ride control system, no loadbalancing is provided between the accumulator and the base end of theactuator. Upon activating the ride control system, the actuator willextend or retract (and thus move the implement and load) unless thepressure at the base end of the actuator is equal to that of theaccumulator.

It will be appreciated that this background description has been createdby the inventor to aid the reader, and is not to be taken as anindication that any of the indicated problems were themselvesappreciated in the art. While the described principles can, in someaspects and embodiments, alleviate the problems inherent in othersystems, it will be appreciated that the scope of the protectedinnovation is defined by the attached claims, and not by the ability ofany disclosed feature to solve any specific problem noted herein.

SUMMARY

The present disclosure, in one aspect, is directed to embodiments of ahydraulic ride control system configured to control the hydraulicpressure of an accumulator based upon pressure differences between ahydraulic actuator and an accumulator. In another aspect, the presentdisclosure is directed to a hydraulic balancing valve that isparticularly useful with a ride control system. In a further aspect, thepresent disclosure is directed to a method of operating a hydraulic ridecontrol system using a hydraulic balancing valve.

In still another aspect, a hydraulic balancing valve includes a body, aspool and a biasing member. The body defines a bore, a charge port, apump port, a tank port, and a control port, with each of the chargeport, the pump port, the tank port, and the control port being in fluidcommunication with the bore. The spool is movably disposed within thebore for directing hydraulic fluid between the charge port and the pumpport and between the charge port and the tank port. The spool includes afirst pressure surface in fluid communication with the charge port and asecond pressure surface in fluid communication with the control port,the first and second pressure surfaces facing in opposing relationshipto each other. The spool is movable within the bore between: a firstposition in which the charge port and the tank port are in fluidcommunication with each other and the charge port and the pump port arein fluid isolation from each other, a second position in which thecharge port, the tank port, and the pump port are in fluid isolationfrom each other, and a third positon in which the charge port and thepump port are in fluid communication with each other and the charge portand the tank port are in fluid isolation from each other. The biasingmember is operatively connected to the body and spool to bias the spoolto the second position and is configured to permit movement of the spoolto the first position upon a first pressure differential between thefirst pressure surface and the second pressure surface and to permitmovement of the spool to the third position upon a second pressuredifferential between the first pressure surface and the second pressuresurface, with the second pressure differential being different from thefirst pressure differential.

In still a further aspect, a hydraulic ride control system includes ahydraulic cylinder, a reservoir of hydraulic fluid, an accumulator, apump, a first control valve, a second control valve, and a hydraulicbalancing valve. The hydraulic cylinder has a chamber, a rod end, and abase end. The reservoir of hydraulic fluid has a first fluidcommunication passage between the rod end of the hydraulic cylinder andthe reservoir. The accumulator has a second fluid communication passagebetween the base end of the hydraulic cylinder and the accumulator. Thepump has a third fluid communication passage between the pump and theaccumulator. The first control valve is disposed along the first fluidcommunication passage to control fluid communication between the rod endof the hydraulic cylinder and the reservoir. The second control valve isdisposed along the second fluid communication passage to control fluidcommunication between the base end of the hydraulic cylinder and theaccumulator. The hydraulic balancing valve includes a body, a spool anda biasing member. The body defines a bore, a charge port, a pump port, atank port, and a control port, with each of the charge port, the pumpport, the tank port, and the control port being in fluid communicationwith the bore. The spool is movably disposed within the bore fordirecting hydraulic fluid between the charge port and the pump port andbetween the charge port and the tank port. The spool includes a firstpressure surface in fluid communication with the charge port and asecond pressure surface in fluid communication with the control port,the first and second pressure surfaces facing in opposing relationshipto each other. The spool is movable within the bore between: a firstposition in which the charge port and the tank port are in fluidcommunication with each other and the charge port and the pump port arein fluid isolation from each other, a second position in which thecharge port, the tank port, and the pump port are in fluid isolationfrom each other, and a third positon in which the charge port and thepump port are in fluid communication with each other and the charge portand the tank port are in fluid isolation from each other. The biasingmember is operatively connected to the body and spool to bias the spoolto the second position and is configured to permit movement of the spoolto the first position upon a first pressure differential between thefirst pressure surface and the second pressure surface and to permitmovement of the spool to the third position upon a second pressuredifferential between the first pressure surface and the second pressuresurface, with the second pressure differential being different from thefirst pressure differential. The accumulator is in fluid communicationwith the charge port. The pump is in fluid communication with the pumpport. The reservoir is in fluid communication with the tank port. Thebase end of the hydraulic cylinder is in fluid communication with thecontrol port.

In an additional aspect, a method of operating a hydraulic balancingvalve includes providing the hydraulic balancing valve, which includes abody, a spool, and a biasing member. The body defines a bore, a chargeport, a pump port, a tank port, and a control port, with each of thecharge port, the pump port, the tank port, and the control port being influid communication with the bore. The spool is movably disposed withinthe bore for directing hydraulic fluid between the charge port and thepump port and between the charge port and the tank port. The spoolincludes a first pressure surface in fluid communication with the chargeport and a second pressure surface in fluid communication with thecontrol port, the first and second pressure surfaces facing in opposingrelationship to each other. The spool is movable within the borebetween: a first position in which the charge port and the tank port arein fluid communication with each other and the charge port and the pumpport are in fluid isolation from each other, a second position in whichthe charge port, the tank port, and the pump port are in fluid isolationfrom each other, and a third positon in which the charge port and thepump port are in fluid communication with each other and the charge portand the tank port are in fluid isolation from each other. The biasingmember being operatively connected to the body and spool to bias thespool to the second position. The method further includes providing afirst charge port pressure at the charge port and a first control portpressure at the control port, with the first charge port pressure andthe first control port pressure being equal and the biasing membermaintaining the spool at the second position, providing a second chargeport pressure at the charge port and a second control port pressure atthe control port, with the second charge port pressure being greaterthan the second control port pressure to define a first pressuredifferential between the charge port and the control port, and the firstpressure differential moving the spool from the second position to thefirst position, and providing a third charge port pressure at the chargeport and a third control port pressure at the control port, with thethird charge port pressure being less than the third control portpressure to define a second pressure differential between the chargeport and the control port, and the second pressure differential movingthe spool from the second position to the third position.

Further and alternative aspects and features of the disclosed principleswill be appreciated from the following detailed description and theaccompanying drawings. As will be appreciated, the hydraulic valves,hydraulic circuits, and methods for controlling hydraulic fluiddisclosed herein are capable of being carried out in other and differentembodiments, and capable of being modified in various respects.Accordingly, it is to be understood that both the foregoing generaldescription and the following detailed description are exemplary andexplanatory only and do not restrict the scope of the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is schematic view of an embodiment of a hydraulic circuit inaccordance with principles of the present disclosure.

FIG. 2 is a cross-sectional view of an embodiment of a balancing valvein accordance with principles of the present disclosure.

FIG. 3 is a cross-sectional view of the balancing valve of FIG. 2 withthe spool in a first pressure imbalance position.

FIG. 4 is a cross-sectional view of the balancing valve of FIG. 2 withthe spool in a second pressure imbalance position.

It should be understood that the drawings are not necessarily to scaleand that the disclosed embodiments are illustrated diagrammatically andin partial views. In certain instances, details which are not necessaryfor an understanding of this disclosure or which render other detailsdifficult to perceive may have been omitted. It should be understoodthat this disclosure is not limited to the particular embodimentsillustrated herein.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Embodiments of a hydraulic ride control system, and a balancing valvefor use therein, constructed in accordance with principles of thepresent disclosure are adapted to control the flow of hydraulic fluidbetween an accumulator and one or more hydraulic cylinders of a materialmoving machine, such as, a skid steer loader, for example. Embodimentsof a hydraulic ride control system constructed in accordance withprinciples of the present disclosure can have the same or similarfunctionality as conventional circuits, but with reduced cost andcomplexity.

Embodiments of a hydraulic ride control system constructed in accordancewith principles of the present disclosure can include a pair ofactuatable control valves. In embodiments, a balancing valve can beprovided to control the flow of hydraulic fluid so that ports of thebalancing valve are fluidly connected to a pump, an accumulator, a tankand a hydraulic cylinder. In embodiments, the balancing valve isconfigured to prevent the flow through two of the ports of the cartridgevalve that are fluidly connected to the pump and the tank when thepressure at two other ports of the cartridge valve that are fluidlyconnected to the accumulator and the hydraulic cylinder is equal. Upon apressure imbalance between the ports fluidly connected to theaccumulator and the hydraulic cylinder, flow is permitted between theport fluidly connected to the accumulator and one of the ports fluidlyconnected to the pump or the tank until the pressure at the two portsfluidly connected to the accumulator and the hydraulic cylinder isequal.

Embodiments of a hydraulic balancing valve constructed in accordancewith principles of the present disclosure are adapted to control theflow of hydraulic fluid such as between an accumulator and one or morehydraulic cylinders operatively associated with a linkage of a materialmoving machine (e.g., skid steer loaders, telehandlers, wheel loaders,tractors, etc.). Embodiments of a hydraulic balancing valve constructedin accordance with principles of the present disclosure can prevent theflow through two of the ports of the balancing valve when the pressureat two balancing ports of the control valve are equal. Upon an imbalancebetween the two balancing ports, flow can be permitted between one ofthe balancing ports and one of the other ports until the flow at thebalancing ports is equal.

Turning now to the Figures, an embodiment of a hydraulic ride controlsystem 10 constructed according to the principles of the presentdisclosure is shown in FIG. 1. In embodiments, the hydraulic ridecontrol system 10 can be used to control the position of one or morehydraulic cylinders 11 used to move the lift arm or arms (not shown) ofa material moving machine such as a skid steer loader (not shown). Inembodiments, the hydraulic cylinders can be any suitable hydrauliccylinder that is acceptable for the intended application, as will bereadily understood by one skilled in the art. In embodiments, thehydraulic cylinders 11 can be double acting cylinders with a rod end 12and a head or base end 13.

A hydraulic ride control system 10 constructed according to principlesof the present disclosure is adapted to be used to control the movementof the hydraulic cylinders 11 such as by reducing undesired movement ofthe cylinders during a material moving operation. More specifically, thehydraulic ride control system 10 can operate to maintain the position ofthe lift arms operatively connected to the hydraulic cylinders 11 as themachine is moved from a dig or load location to a dump location.

As depicted, the hydraulic ride control system 10 is operativelyconnected to the hydraulic cylinders 11 as well as a pump 15, anaccumulator 16, and a tank 17. The hydraulic ride control system 10comprises a first control valve 20, a second control valve 25, and abalancing control valve 30.

In embodiments, the pump 15 can be any suitable pump that it isacceptable for the intended application, as will be readily understoodby one skilled in the art. In embodiments, the pump 15 can be afixed-displacement pump or a variable-displacement pump. The pump 15 isin fluid communication with the balancing control valve 30 via a supplyline 150. In embodiments, a flow orifice 165 and a check valve 166 canbe positioned along the supply line 150. In embodiments, the floworifice 165 can be any suitable flow orifice that is acceptable for theintended application, as will be readily understood by one skilled inthe art. In embodiments, the flow orifice 165 operates to control theflow rate of hydraulic fluid along the supply line 150. In embodiments,the check valve 166 can be any suitable check valve that is acceptablefor the intended application, as will be readily understood by oneskilled in the art. In embodiments, the check valve 166 can operate toprevent flow of hydraulic fluid through the supply line 150 if thepressure in the supply line is less than a predetermined threshold.

The pump 15 can be in fluid communication with the tank 17 via anysuitable technique. As depicted, the pump 15 is in fluid communicationwith the tank 17 via a pump supply line 151.

In embodiments, the accumulator 16 can be any suitable accumulator thatit is acceptable for the intended application, as will be readilyunderstood by one skilled in the art. In embodiments, the accumulator 16can receive hydraulic fluid and utilize a compressible gas such asnitrogen to adjust the pressure of the accumulator. The accumulator 16is in fluid communication with the balancing control valve 30 via anaccumulator line 152 and an accumulator control line 153. In addition,the accumulator 16 is in fluid communication with the second controlvalve 25 via the accumulator line 152 and an accumulator valve line 154.In embodiments, the tank 17 can be any suitable tank that it isacceptable for the intended application, as will be readily understoodby one skilled in the art. In embodiments, the tank 17 comprises areservoir of hydraulic fluid which can be drawn into the pump 15 throughpump supply line 151. In addition, the tank 17 is in fluid communicationwith the first control valve 20 via the tank line 155 and with thebalancing control valve 30 via tank control line 156.

In embodiments, the first control valve 20 can be any suitable valvethat it is acceptable for the intended application, as will be readilyunderstood by one skilled in the art. In embodiments, the first controlvalve 20 can be a two position valve movable between a first position 21and a second position 22. A solenoid assembly 23 can be adapted toselectively move the first control valve 20 between the first position21 and the second position 22. In embodiments, the first control valve20 can include one or more biasing members 24, such as a spring, to biasthe first control valve to the first position 21. Other manners ofactuating the first control valve 20 are contemplated.

The first control valve 20 is in fluid communication with the tank 17via the tank line 155. The first control valve 20 is also in fluidcommunication with the rod end 12 of the hydraulic cylinder 11 via a rodend line 157.

At the first position 21, flow of hydraulic fluid is permitted in onlyone direction from the tank line 155 to the rod end 12 of the hydrauliccylinder 11 via rod end line 157. As a result, when in the firstposition 21, hydraulic fluid may not flow from the rod end 12 ofhydraulic cylinder 11 to the tank 17. At the second position 22,hydraulic fluid may flow in both directions through the first controlvalve 20 between the tank line 155 and the rod end line 157 and thusbetween the rod end 12 of the hydraulic cylinder 11 and the tank 17.

In embodiments, the second control valve 25 can be any suitable valvethat it is acceptable for the intended application, as will be readilyunderstood by one skilled in the art. In embodiments, the second controlvalve 25 can be a two position valve movable between a first position 26and a second position 27. A solenoid assembly 28 can be adapted toselectively move the second control valve 25 between the first position26 and the second position 27. In embodiments, the second control valve25 can include one or more biasing members 29, such as a spring, forexample, to bias the second control valve to the first position 26.Other manners of actuating the second control valve 25 are contemplated.

The second control valve 25 is in fluid communication with theaccumulator 16 via the accumulator line 152 and the accumulator valveline 154. The second control valve 25 is also in fluid communicationwith the base end 13 of the hydraulic cylinder 11 via a base end line158 and with the balancing control valve 30 via base end control line159.

At the first position 26, flow of hydraulic fluid is blocked fromflowing between the accumulator valve line 154 and the base end line158. As a result, when in the first position 26, hydraulic fluid may notflow between the base end 13 of hydraulic cylinder 11 and theaccumulator 16 in either direction. At the second position 27, hydraulicfluid may flow in both directions through the second control valve 25between the accumulator valve line 154 and the base end line 158.

In embodiments, the balancing control valve 30 can be any suitable valvethat it is acceptable for the intended application, as will be readilyunderstood by one skilled in the art. In embodiments, the balancingcontrol valve 30 can be a cartridge-type mechanical valve having fourports with flow through the valve controlled by the pressure at certainof the ports. As depicted, the first port 171 is in fluid communicationwith the accumulator control line 153 and may be referred to herein asthe charge port, the second port 172 is in fluid communication with thesupply line 150 and may be referred to herein as the pump port, thethird port 173 is in fluid communication with the tank control line 156and may be referred to herein as the tank port, and the fourth port 174is in fluid communication with the base end control line 159 and may bereferred to herein as the control port.

Referring to FIG. 2, the balancing control valve 30 includes a cage 31,which is hollow and generally cylindrical, and a spool 55, which isgenerally cylindrical and slidably disposed within the cage. The cage 31has a first end 32 and a second end 33, which is opposite the first end32. The cage 31 defines a central bore 34 that extends along alongitudinal axis of the cage and between the first and second ends 32,33.

In embodiments, an outer surface 35 of cage 31 can be adapted to besealingly engaged with a suitable, mating valve body or housing (notshown). The illustrated outer surface 35 includes a pair of sealingsections 36 that are in spaced relationship to each other. Each sealingsection 36 includes an annular groove 37 configured to receive therein asuitable annular sealing member such as a D-ring 180. The outer surface35 of the cage 31 is stepped generally adjacent the second end 33 andincludes an annular stop section 40 having an enlarged diameter spacedfrom the second end defining an annular stop surface or shoulder 41. Theouter surface 35 of the cage 31 further includes a first annular sealingand locking surface 42 that extends from the second end 33 towards thefirst end 32 and a second annular surface 43 between the annular stopsection 40 and the first annular sealing and locking surface 42. Thefirst annular sealing and locking surface 42 can include an annulargroove 44 configured to receive a locking ring 181 therein.

An opening 45 at the first end 32 of the cage 31 defines the first port171 of the balancing control valve 30. The cage 31 includes a set offirst radial bores 47 that extends between the outer surface 35 and thecentral bore 34 to define the second port 172. The first radial bores 47are disposed in a circumferentially spaced apart relationship relativeto each other around the cage 31.

The cage 31 defines a set of second radial bores 50 that extends betweenthe outer surface 35 and the central bore 34 to define a third port 173.The second radial bores 50 are disposed in a circumferentially spacedapart relationship relative to each other around the cage 31.

The spool 55 has a first end 56 and a second end 57 opposite the firstend 56. An outer surface 60 of the spool 55 includes a first annularland 61 adjacent the first end 56 and a second annular land 62 spacedfrom the first land and disposed generally adjacent a midpoint 58 of thespool. An annular groove 63 is disposed between the first land 61 andthe second land 62.

A central bore 64 extends along an axial centerline of the spool 55 fromthe first end 56 partway towards the second end 57. An end surface ofthe central bore 64 defines a pressure surface 65 operative to move thespool 55 as discussed in further detail below. A set of first spoolradial bores 66 extends between the outer surface 60 of the spool 55adjacent the lower end of the annular groove 63 and the central bore 66.The first spool radial bores 66 are disposed in a circumferentiallyspaced apart relationship relative to each other around the spool 55.

A set of second spool radial bores 67 extends between the outer surface60 of the spool adjacent the upper end of the annular groove 63 and thecentral bore 64. The second spool radial bores 67 are disposed in acircumferentially spaced apart relationship relative to each otheraround the spool 55. The annular groove 63 is in fluid communicationwith the central bore 64 through the first and second spool bores 66,67.

The spool 55 includes, sequentially from the second annular land 62towards the second end 57 of the spool, a first reduced diameter section68, a second reduced diameter section 69, smaller than the first reduceddiameter section, and a tapered end section 70 that extends from thesecond section 69 to the second end 57 of the spool 55. An annularpressure surface or shoulder 71 is defined by the difference in diameterbetween the second annular land 62 and the first reduced diametersection 68. The pressure surface 65 of the central bore 64 and theannular pressure shoulder 71 are in opposing relationship to each otherso that a sufficient pressure differential or imbalance between thepressure at the pressure surface 65 and the pressure at the annularpressure shoulder 71 can cause movement of the spool 55 within the bore34 of the cage 31. An annular engagement shoulder 72 is defined by thedifference in diameter between the first reduced diameter section 68 andthe second reduced diameter section 69. The outer surface 60 of thespool 55 adjacent the intersection between the second reduced diametersection 69 and the tapered end section 70 can include an annular groove73 configured to receive a locking ring 182 therein.

A cap 75 is disposed at the second end 33 of the cage 31 to enclose thebore 34 of the cage. The cap 75 has a first end 76 and a second oppositeend 77 with a stepped bore 78 that extends from the first end towardsthe second end. The bore 34 of the cage 31 and the stepped bore 78 ofthe cap 75 define the bore of the balancing control valve 30. Thestepped bore 78 includes, in sequence from the first end 76 towards thesecond end 77, an enlarged first section 79, a second section 80 havinga smaller diameter than the first section, a third section 81 having asmaller diameter than the second section, and a fourth section 82 havinga smaller diameter than the third section. The first section 79 isconfigured so that a portion thereof engages the second annular surface43 of the outer surface 35 of the cage 31 when the first end 76 of thecap 75 abuts the stop surface 41 of the cage. An additional length ofthe first section 79 is spaced from the first annular sealing andlocking surface 42. A resilient annular seal 183, such as a D-ring, canbe positioned between the first annular sealing and locking surface 42and the first section 79.

The second section 80 of the stepped bore 78 is configured to bedisposed adjacent the first annular sealing and locking surface 42 ofthe outer surface 35 of the cage 31. The second section 80 of thestepped bore 78 can include an annular groove 83 aligned with theannular groove 44 in the first annular sealing and locking surface 42 ofthe cage 31. The locking ring 181 can be positioned in the annulargroove 44 of the first annular surface 42 and the annular groove 83 ofthe second section 80 to retain the cap 75 on the second end 33 of thecage 31.

The smaller diameter of the third section 81 of the stepped bore 78relative to the diameter of the second section 80 defines a spool guideengagement shoulder 84 along the stepped bore. The smaller diameter ofthe fourth section 82 of the stepped bore 78 relative to the diameter ofthe third section 81 defines a biasing guide engagement shoulder 85along the stepped bore.

The outer surface 86 of the cap 75 includes, in sequence from the firstend 76 towards the second end 77, an reduced diameter threaded firstsection 87, a second section 88 having a larger diameter than the firstsection, and a tool engagement section 89 adjacent the second end 77.The larger diameter of the second section 88 of the outer surface 86relative to the diameter of the first section 87 defines a shoulder 90along the outer surface. The outer surface of the first section 87includes an annular recess 91 adjacent the shoulder 90 with resilientannular seal, such as an O-ring 184, disposed therein.

The second section 88 of the outer surface 86 of the cap 75 includes twospaced apart annular grooves. The first annular groove 92 is in fluidcommunication with one or more radial bores 93 that extend between thefirst annular groove and the third section 81 of the stepped bore 78 anddefines a fourth port 174 of the balancing control valve 30. The secondannular groove 95 is positioned between the first annular groove 92 andthe tool engagement section 89. The second annular groove 94 isconfigured to receive therein a suitable annular sealing member such asa suitable O-ring 185 and a support or back-up ring 186.

The tool engagement section 89 of the outer surface 86 of the cap 75 canbe configured with a hexagonal cross-section to facilitate engagementwith a tool to screw the balancing control valve 30 into a bore (notshown) in a valve housing (not shown). Upon mounting the balancingcontrol valve 30 to the valve housing (not shown), the D-ring 180closest to the first end 32 of the cage 31 interacts with the valvehousing to seal the first port 171, the spaced apart pair of D-rings 180interact with the valve housing to seal the second port 172, the D-ring180 spaced from the first end 32 of the cage 31 (i.e., between thesecond port 172 and the third port 173) and the O-ring 184 interact withthe valve housing to seal the third port 173, and the pair of O-rings184, 185 interact with the valve housing to seal the fourth port 174.

An annular spool guide 100 is disposed within the first section 79 ofthe stepped bore 78 of the cap 75. The spool guide 100 includes a firstend 101 and a second end 102 with a central bore 103 extendingtherebetween. The central bore 103 is configured to guide and supportthe first reduced diameter section 68 of the spool 55 as the spoolslides within the cage 31. An enlarged flange 103 at the second end 102of the spool guide 100 is disposed between the second end 33 of the cage31 and the spool guide engagement shoulder 84 within the stepped bore 78of the cap 75 to secure the spool guide within the balancing controlvalve 30.

A biasing guide assembly 105 is disposed within the second and thirdsections 80, 81 of the stepped bore 78 of the cap 75. The biasing guideassembly 105 includes a first annular biasing guide member 106, a secondannular biasing guide member 107 spaced from the first biasing guidemember, and a biasing member 108, such as a compression spring,positioned between the first and second biasing guide members. The firstbiasing guide member 106 includes a first end 110 and a second end 111with a central bore 112 extending therebetween. The central bore 112 isconfigured to guide and support the second reduced diameter section 69of the spool 55 as the spool slides within the cage 31. The first end110 of the first biasing guide member 106 is also configured to engageboth the engagement shoulder 72 of the spool 55 and the second end 102of the spool guide 100. The first biasing guide member 106 can alsoinclude a flange 113 configured to engage the biasing member 108.

The second biasing guide member 107 includes a first end 115 and asecond end 116 with a central bore 117 extending therebetween. Thecentral bore 117 is configured to guide and support the second reduceddiameter section 69 of the spool 55 as the spool slides within the cage31. The second biasing guide member 107 can also include a flange 118configured to engage the biasing member 108 on one side of the flangeand engage the biasing guide engagement shoulder 85 of the stepped bore78 of the cap 75 on an opposite side of the flange. The second end 116of the second biasing guide member 107 is also configured to engage thelocking ring 182 disposed within the annular groove 73 at theintersection between the second reduced diameter section 69 and thetapered end section 70.

Although the first and second biasing guide members 106, 107 areconfigured identically, in embodiments, other configurations arecontemplated. For example, as depicted, the biasing member 108 isdisposed between the flange 113 of the first biasing guide member 106and the flange 118 of the second biasing guide member 107. In anotherconfiguration, the biasing member 108 can be secured or fixed to thefirst and second biasing guide members 106, 107.

In embodiments, the annular spool guide 100 and the biasing guideassembly 105 are configured to permit fluid communication from the thirdsection 81 of the stepped bore 78 and the fourth section 82 of thestepped bore to the pressure shoulder 71 at the first reduced diametersection 68 of the spool 55. More specifically, sufficient clearanceexists between the second reduced diameter section 69 of the spool 55and the central bore 117 of the second biasing guide member 107 topermit hydraulic fluid within the fourth port 174 to flow between thesecond reduced diameter section 69 of the spool 55 and the central boreof the second biasing guide member 107 so that fluid can pass betweenthe third and fourth sections 81, 82 of the stepped bore 78. In analternate or additional embodiment, the spool 55 and/or the secondbiasing guide member 107 may include passages (not shown) to permit theflow of hydraulic fluid between the third section 81 of the stepped bore78 and the fourth section 82 of the stepped bore.

In addition, hydraulic fluid within the fourth port 174 can flow betweenthe second reduced diameter section 69 of the spool 55 and the firstbiasing guide member 106 and between the first reduced diameter section68 of the spool and the spool guide 100 to reach the pressure shoulder71 at the first reduced diameter section 68 of the spool. In analternate or additional embodiment, the spool 55, the spool guide 100,and/or the first biasing guide member 106 may include passages (notshown) to permit the flow of hydraulic fluid from the third section 81of the stepped bore 78 to the second section 82 of the stepped bore.

The balancing control valve 30 is configured so that the spool 55 isbiased by the biasing guide assembly 105 to a fully closed position inwhich the flow of hydraulic fluid within or through the balancingcontrol valve is blocked or prevented. More specifically, as depicted inFIG. 2, the cage 31, the spool 55, the cap 75, the spool guide 100, andthe biasing guide assembly 105 are configured so that when the pressurebetween the first port 171 and the fourth port 174 are equal, the spoolis positioned to block the flow of hydraulic fluid between the firstport 171 and the second port 172 and between the first port 171 and thethird port 173. Since the balancing control valve 30 is in its neutralor closed position when the pressures at the first port 171 and thefourth port 174 are equal, the first port and the fourth port aresometimes referred to herein as the balancing ports. It should be notedthat, as configured, the fourth port 174 is never in fluid communicationwith the first, second, or third ports 171, 172, 173 through thebalancing control valve 30.

A difference in hydraulic pressure between the balancing ports (firstport 171 and fourth port 174) will cause the spool 55 to shift or moveupwards or downwards (as oriented in FIG. 2) to the position depicted inFIG. 3. More specifically, the first port 171 is in fluid communicationwith the pressure surface 65 of the central bore 64 and the fourth port174 is in fluid communication with the annular pressure shoulder 71.Accordingly, if the pressure at the first port 171 is greater than thepressure at the fourth port 174, the pressure at the pressure surface 65will be greater than the pressure at the annular pressure shoulder 71causing the spool 55 to shift or move upwards. Upon moving the spool 55upwards, the first reduced diameter section 68 of the spool 55 slidesupwards within the spool guide 100. As the spool 55 moves upwards, theinteraction between the engagement shoulder 72 of the spool with thefirst end 110 of the first biasing guide member 106 of the biasing guideassembly 105 causes the first biasing guide member 106 to move towardsthe second biasing guide member 107 and compresses the biasing member108. The upward movement of the spool 55 also causes the upper end ofthe annular groove 63 of the spool 55 to become aligned with the thirdport 173. Since the annular groove 63 is in fluid communication with thefirst port 45 through the central bore 64 of the spool 55 and the firstand second radial spool bores 66, 67, the first port is thus in fluidcommunication with the third port 173.

If the pressure at the first port 171 is less than the pressure at thefourth port 174, pressure at the pressure surface 65 will be less thanthe pressure at the annular pressure shoulder 71 causing the spool 55 toshift or move downwards to the position depicted in FIG. 4. Upon movingthe spool 55 downwards, the first reduced diameter section 68 of thespool 55 slides downward within the spool guide 100 and the interactionbetween the locking ring 182 at the intersection of the second reduceddiameter section 69 and the tapered end section 70 of the spool 55 withthe second end 116 of the second biasing guide member 107 causes thesecond biasing guide member to move towards the first biasing guidemember 106 and compresses the biasing member 108. The downward movementof the spool 55 also causes the lower end of the annular groove 63 ofthe spool 55 to become aligned with the second port 172 and thusestablish fluid communication between the first port 45 and the secondport through the central bore 64 of the spool 55.

As used herein, the balancing control valve 30 is sometimes referred toas a mechanical balancing control valve because the movement or controlof the spool 55 within the cage 31 is controlled or caused by the springforce of the biasing member 105 and the pressure of the hydraulic fluidat the first and fourth ports 171, 174 as opposed to a solenoid assemblyoperating in conjunction with a biasing member in a manner similar tothe first and second control valves 20, 25.

Referring to FIG. 1 in conjunction with FIG. 2, the first control valve20 is depicted at its first position 21 and the second control valve 25is depicted at its first position 26. Accordingly, the flow of hydraulicfluid from the rod end 12 of the hydraulic cylinder 11 to the tank 17 isprevented as is the flow of hydraulic fluid from the base end 13 of thehydraulic cylinder to the actuator 16. In such a configuration, thepressure at the first port 171 from the accumulator 16 equals thepressure at the fourth port 174 from the base end 13 of the hydrauliccylinder 11 so that the spool 55 will remain at its neutral or closedposition as depicted in FIG. 2. As a result, the flow of hydraulic fluidfrom the pump 15 through the second port 172 and to the tank 17 throughthe third port 173 is prevented.

Upon operating the machine to perform a material lifting operationthrough the use of additional hydraulic circuitry (not shown)operatively connected to the hydraulic cylinders 11, the pressure at thebase end 13 of the hydraulic cylinders will increase. The increase inpressure at the base end 13 of the hydraulic cylinders 11 increases thepressure at the fourth port 174 without a similar increase in pressureat the accumulator 16, and thus the first port 171. The resultingpressure differential between the first port 171 and the fourth port 174causes the spool 55 to move downward (i.e., towards the first end 32 ofthe cage 31) which results in a portion of the annular groove 63becoming aligned with the second port 172 (FIG. 4). As a result of thefluid communication between the annular groove 63 and the central bore64, the first port 171 and the second port 172 are in fluidcommunication. The fluid communication between the first port 171 andthe second port 172 permits hydraulic fluid to flow from the pump 15through the second port to first port and then to the accumulator 16.Such fluid flow increases the pressure at the accumulator 16 andcontinues until the pressure at the accumulator equals the pressure atthe base end 13 of the hydraulic cylinders 11, causing the spool 55 toshift upwards to the neutral or closed position as depicted in FIG. 2.

To activate the hydraulic ride control system 10, each of the firstcontrol valve 20 and the second control valve 25 are shifted to theirrespective second positions 22, 27. With the hydraulic ride controlsystem 10 activated, hydraulic fluid can flow from the rod end 12 of thehydraulic cylinders 11 sequentially through the rod end line 157, thefirst control valve 20, and the tank line 155 to the tank 17. Inaddition, hydraulic fluid can flow from the base end 13 of the hydrauliccylinders 11 sequentially through the base end line 158, the secondcontrol valve 25, the accumulator valve line 154, and the accumulatorline 152 to the accumulator 16.

Further, with the hydraulic ride control system 10 activated, the firstport 171 and the fourth port 174 of the balancing control valve 30 arefluidly connected through the second control valve 25. As a result, thebalancing control valve 30 is maintained at its neutral or closedposition (as depicted in FIG. 2) with no hydraulic fluid passing throughthe second port 172 or the third port 173. Through such a configuration,the base end 12 of the hydraulic cylinders 11 is fluidly connected tothe accumulator 16 to provide the desired ride control functionality.

As the machine on which the hydraulic ride control system 10 is disposedmoves about the work site, a work implement operatively connected to thehydraulic cylinders 11 may tend to move up and down due to bumps andunevenness in the terrain. This movement of the work implement will tendto cause changes in the pressure at the base end 13 of the hydrauliccylinders 11. The change in pressure at the base end 13 of the hydrauliccylinders 11 will cause a pressure imbalance between the first port 171and the fourth port 174 of the balancing control valve 30. As a result,there will be a pressure imbalance between the pressure surface 65 ofthe central bore 64 and the annular pressure shoulder 71. Depending uponwhether the pressure is greater at the pressure surface 65 or thepressure shoulder 71, the spool 55 will move within the bore to fluidlyconnect either the first port 171 with the second port 172 or fluidlyconnect the first port 171 with the third port 173 to increase ordecrease the pressure at the accumulator 16 until there is pressurebalance between the first port 171 and the fourth port 174.

Upon or immediately prior to dumping a load of material at a dumplocation, the hydraulic ride control system 10 is deactivated and eachof the first control valve 20 and the second control valve 25 areshifted to their respective first positions 21, 26. In doing so, thefirst port 171 and the fourth port 174 are no longer in fluidcommunication through the second control valve 25. As a result, upondumping the load of material, the pressure at the base end 13 of thehydraulic cylinders 11 (and thus at the fourth port 174) is greater thanthe pressure at the accumulator 16 (and thus at the first port 171). Theresulting pressure differential between the first port 171 (togetherwith pressure surface 65) and the fourth port 174 (together withpressure shoulder 71) causes the spool 55 to move upward (i.e., towardsthe second end 33 of the cage 31) which results in a portion of theannular groove 63 becoming aligned with the third port 173 as depictedin FIG. 3. As a result of the fluid communication between the annulargroove 63 and the central bore 64, the first port 171 and the third port173 are in fluid communication. The fluid communication between thefirst port 171 and the third port 173 permits hydraulic fluid to flowfrom the accumulator 16 through the first port to third port and then tothe tank 17. Such fluid flow decreases the pressure at the accumulator16 and continues until the pressure at the accumulator equals thepressure at the base end 13 of the hydraulic cylinders 11, causing thespool 55 to shift downward to the neutral or closed position as depictedin FIG. 2.

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedto be incorporated by reference and were set forth in its entiretyherein.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. Recitation of ranges of valuesherein are merely intended to serve as a shorthand method of referringindividually to each separate value falling within the range, unlessotherwise indicated herein, and each separate value is incorporated intothe specification as if it were individually recited herein. All methodsdescribed herein can be performed in any suitable order unless otherwiseindicated herein or otherwise clearly contradicted by context. The useof any and all examples, or exemplary language (e.g., “such as”)provided herein, is intended merely to better illuminate the inventionand does not pose a limitation on the scope of the invention unlessotherwise claimed. No language in the specification should be construedas indicating any non-claimed element as essential to the practice ofthe invention.

Preferred embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention.Variations of those preferred embodiments may become apparent to thoseof ordinary skill in the art upon reading the foregoing description. Theinventors expect skilled artisans to employ such variations asappropriate, and the inventors intend for the invention to be practicedotherwise than as specifically described herein. Accordingly, thisinvention includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

What is claimed is:
 1. A hydraulic balancing valve, comprising: a body,the body defining a bore, a charge port, a pump port, a tank port, and acontrol port, each of the charge port, the pump port, the tank port, andthe control port being in fluid communication with the bore; a spool,the spool being movably disposed within the bore for directing hydraulicfluid between the charge port and the pump port and between the chargeport and the tank port, the spool including a first pressure surface influid communication with the charge port and a second pressure surfacein fluid communication with the control port, the first and secondpressure surfaces facing in opposing relationship to each other, thespool being movable within the bore between: a first position in whichthe charge port and the tank port are in fluid communication with eachother and the charge port and the pump port are in fluid isolation fromeach other, a second position in which the charge port, the tank port,and the pump port are in fluid isolation from each other, and a thirdpositon in which the charge port and the pump port are in fluidcommunication with each other and the charge port and the tank port arein fluid isolation from each other; and a biasing member, the biasingmember operatively connected to the body and spool to bias the spool tothe second position and configured to permit movement of the spool tothe first position upon a first pressure differential between the firstpressure surface and the second pressure surface and to permit movementof the spool to the third position upon a second pressure differentialbetween the first pressure surface and the second pressure surface, thesecond pressure differential being different from the first pressuredifferential.
 2. The hydraulic balancing valve of claim 1, wherein thespool is disposed at the second position upon a pressure balance betweenthe first pressure surface and the second pressure surface, the spool isdisposed at the first position at the first pressure differential, andthe spool is disposed at the third position at the second pressuredifferential.
 3. The hydraulic balancing valve of claim 2, wherein atthe first pressure differential, a pressure at the charge port isgreater than a pressure at the control port, and at the second pressuredifferential, the pressure at the charge port is less than a pressure atthe control port.
 4. The hydraulic balancing valve of claim 1, whereinthe body comprises a cage and a cap disposed on the cage, a firstportion of the bore being defined by the cage and a second portion ofthe bore being defined by the cap.
 5. The hydraulic balancing valve ofclaim 4, wherein the control port extends through the cap into the bore.6. The hydraulic balancing valve of claim 1, wherein the spool includesa central bore and an annular groove in fluid communication with thecentral bore, a first portion of the annular groove being in fluidcommunication with the pump port in the first position and a secondportion of the annular groove being in fluid communication with the tankport in the third position.
 7. The hydraulic balancing valve of claim 6,wherein the first and second portions of the annular groove are axiallyspaced apart along the spool.
 8. The hydraulic balancing valve of claim6, wherein the spool includes a plurality of spool bores between thecentral bore and the annular groove.
 9. The hydraulic balancing valve ofclaim 6, wherein the charge port is aligned with the central bore of thespool.
 10. The hydraulic balancing valve of claim 6, wherein the firstpressure surface is disposed within the central bore of the spool. 11.The hydraulic balancing valve of claim 10, wherein the second pressuresurface comprises an annular surface.
 12. The hydraulic balancing valveof claim 11, wherein the annular surface extends about an outer surfaceof the spool.
 13. The hydraulic balancing valve of claim 1, wherein thebiasing member is disposed within a portion of the bore in fluidcommunication with the control port.
 14. The hydraulic balancing valveof claim 1, further comprising first and second annular biasing guidemembers, the first and second annular biasing guide members having acentral bore with the spool movably disposed within the central bore ofeach biasing guide member.
 15. The hydraulic balancing valve of claim14, wherein the biasing member extends between the first and secondbiasing guide members.
 16. The hydraulic balancing valve of claim 1,wherein the bore includes a first end and a second end, and in the firstposition, the spool is displaced from the second position towards thesecond end of the bore and in the third position, the spool is displacedfrom the second position towards the first end of the bore.
 17. Thehydraulic balancing valve of claim 16, wherein the first end of the boreis disposed generally adjacent the charge port.
 18. The hydraulicbalancing valve of claim 16, further comprising first and second biasingguide members disposed within the bore of the body, each of the firstand second biasing guide members being spaced apart in a neutralposition when the spool is in the second position, the first biasingguide member being displaced from the neutral position towards thesecond end of the bore and the second biasing guide member engaging afirst shoulder within the bore when the spool is in the first position,and the first biasing guide member engaging a second shoulder within thebore and the second biasing guide member being displaced from theneutral position towards the first end of the bore when the spool is inthe third position.
 19. The hydraulic balancing valve of claim 18,wherein the first and second biasing guide members each have a centralbore and the spool is movably disposed within the central bore of eachbiasing guide member.
 20. The hydraulic balancing valve of claim 18,wherein the first and second biasing guide members are adjacent eachother when the spool is in at least one of the first configuration andthe third configuration.
 21. The hydraulic balancing valve of claim 1,wherein the body comprises an elongated cylindrical cage and a capdisposed on the cage, the bore extends along a longitudinal axis of thecage, and the first port is disposed along the longitudinal axis.
 22. Ahydraulic ride control system comprising: a hydraulic cylinder having achamber, a rod end, and a base end; a reservoir of hydraulic fluid witha first fluid communication passage between the rod end of the hydrauliccylinder and the reservoir; an accumulator with a second fluidcommunication passage between the base end of the hydraulic cylinder andthe accumulator; a pump with a third fluid communication passage betweenthe pump and the accumulator; a first control valve disposed along thefirst fluid communication passage to control fluid communication betweenthe rod end of the hydraulic cylinder and the reservoir; a secondcontrol valve disposed along the second fluid communication passage tocontrol fluid communication between the base end of the hydrauliccylinder and the accumulator; a hydraulic balancing valve comprising: abody, the body defining a bore, a charge port, a pump port, a tank port,and a control port, each of the charge port, pump port, tank port, andcontrol port being in fluid communication with the bore; a spool, thespool being movably disposed within the bore for directing hydraulicfluid between the charge port and the pump port and between the chargeport and the tank port, the spool including a first pressure surface influid communication with the charge port and a second pressure surfacein fluid communication with the control port, the first and secondpressure surfaces facing in opposing relationship to each other, thespool being movable within the bore between: a first position in whichthe charge port and the tank port are in fluid communication with eachother and the charge port and the pump port are in fluid isolation fromeach other, a second position in which the charge port, the tank port,and the pump port are in fluid isolation from each other, and a thirdpositon in which the charge port and the pump port are in fluidcommunication with each other and the charge port and the tank port arein fluid isolation from each other; and a biasing member, the biasingmember operatively connected to the body and spool to bias the spool tothe second position and configured to permit movement of the spool tothe first position upon a first pressure differential between the firstpressure surface and the second pressure surface and to permit movementof the spool to the third position upon a second pressure differentialbetween the first pressure surface and the second pressure surface, thesecond pressure differential being different from the first pressuredifferential; and the accumulator being in fluid communication with thecharge port; the pump being in fluid communication with the pump port;the reservoir being in fluid communication with the tank port; and thebase end of the hydraulic cylinder being in fluid communication with thecontrol port.
 23. The hydraulic ride control system of claim 22, whereinthe body comprises an elongated cylindrical cage and a cap disposed onthe cage, the bore extends along a longitudinal axis of the cage, andthe first port is disposed along the longitudinal axis.
 24. A method ofoperating a hydraulic balancing valve, comprising: providing thehydraulic balancing valve, the hydraulic balancing valve including abody, a spool, and a biasing member, the body defining a bore, a chargeport, a pump port, a tank port, and a control port, each of the chargeport, pump port, tank port, and control port being in fluidcommunication with the bore, the spool being movably disposed within thebore for directing hydraulic fluid between the charge port and the pumpport and between the charge port and the tank port, the spool includinga first pressure surface in fluid communication with the charge port anda second pressure surface in fluid communication with the control port,the first and second pressure surfaces facing in opposing relationshipto each other, the spool being movable within the bore between a firstposition in which the charge port and the tank port are in fluidcommunication with each other and the charge port and the pump port arein fluid isolation from each other, a second position in which thecharge port, the tank port, and the pump port are in fluid isolationfrom each other, and a third positon in which the charge port and thepump port are in fluid communication with each other and the charge portand the tank port are in fluid isolation from each other, and thebiasing member being operatively connected to the body and spool to biasthe spool to the second position; providing a first charge port pressureat the charge port and a first control port pressure at the controlport, the first charge port pressure and the first control port pressurebeing equal and the biasing member maintaining the spool at the secondposition; providing a second charge port pressure at the charge port anda second control port pressure at the control port, the second chargeport pressure being greater than the second control port pressure todefine a first pressure differential between the charge port and thecontrol port, the first pressure differential moving the spool from thesecond position to the first position; and providing a third charge portpressure at the charge port and a third control port pressure at thecontrol port, the third charge port pressure being less than the thirdcontrol port pressure to define a second pressure differential betweenthe charge port and the control port, the second pressure differentialmoving the spool from the second position to the third position.